Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. X. Optical Variability Characteristics

We compiled a sample of 73 active galactic nuclei (AGNs) with reverberation mapping (RM) observations from RM campaigns, including our ongoing campaign of monitoring super-Eddington accreting massive black holes (BHs). This sample covers a large range of BH mass (M. = 10(6-9) M-circle dot), dimensionless accretion rates ((M) over dot = 10(-)(2.)(7)-10(2.7)), and 5100 angstrom luminosity (L-5100 = 10(42-46) erg s(-1)), allowing us to systematically study the AGN variability and their relations with BH mass, accretion rates, and optical luminosity. We employed the damped random walk (DRW) model to delineate the optical variability of continuum at 5100 angstrom and obtained damped variability timescale (tau(d)) and amplitude (sigma(d)) using a Markov Chain Monte Carlo method. We also estimated the traditional variability amplitudes (F-var), which provide a model-independent measure and therefore are used to test the DRW results. We found that AGN variability characteristics are generally correlated with (M., (M) over dot, L-5100). These correlations are smooth from sub-Eddington to super-Eddington accretion AGNs, probably implying that the AGN variability may be caused by the same physical mechanism.